Switch from travis to github workflows

.github/workflows/ci.yml

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+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ${{matrix.os}}
+    strategy:
+      matrix:
+        os: ["ubuntu-20.04"]
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: olafurpg/setup-scala@v10
+      with:
+        java-version: 8
+    - name: Mount caches
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.sbt
+          ~/.ivy2/cache
+          ~/.cache/coursier
+        key: ${{ runner.os }}-sbt-${{ hashFiles('**/*.sbt') }}
+    - name: Compile and test
+      run: |
+       sbt test
+      shell: bash
+    - name: Format check
+      if: ${{ runner.os == 'Linux' }}
+      run: |
+        sbt scalafmtCheck test:scalafmtCheck scalafmtSbtCheck
+  # Single final job for mergify.
+  ci-passed:
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+    - run: ':'

.github/workflows/release.yml

@@ -0,0 +1,41 @@
+name: Release
+
+on:
+  push:
+    branches: [master]
+    tags: ["v*"]
+
+jobs:
+  publish:
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v1
+    - name: Scala caches
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.sbt
+          ~/.ivy2/cache
+          ~/.cache/coursier
+        key: ${{ runner.os }}-sbt-docs-${{ hashFiles('**/*.sbt') }}
+    - uses: actions/setup-java@v1
+      with:
+        java-version: 8
+    - uses: olafurpg/setup-gpg@v3
+      if: startsWith(github.ref, 'refs/tags/v')
+    - name: "Publish release: ${{github.ref}}"
+      if: startsWith(github.ref, 'refs/tags/v')
+      run: PUBLISH_ONLY=${GITHUB_REF%%/*} RELEASE=1 sbt ci-release
+      env:
+        PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
+        PGP_SECRET: ${{ secrets.PGP_SECRET }}
+        SONATYPE_PASSWORD: ${{ secrets.SONATYPE_PASSWORD }}
+        SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}
+    - name: "Publish snapshot: ${{github.ref}}"
+      if: "!startsWith(github.ref, 'refs/tags/v')"
+      run: sbt ci-release
+      env:
+        PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
+        PGP_SECRET: ${{ secrets.PGP_SECRET }}
+        SONATYPE_PASSWORD: ${{ secrets.SONATYPE_PASSWORD }}
+        SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}